JP3651127B2 - Vehicle behavior control device - Google Patents

Abstract

PROBLEM TO BE SOLVED: To realize stability of a vehicle and decelerating degree desired by a driver by carrying out driving wheel control for regulating braking force of driving wheels under a condition in which the wheel speed of the driving wheel is reduced by an engine brake, and also carrying out driven wheel control for reducing wheel speed of driven wheels. SOLUTION: During running of a vehicle, in a driving force control unit 20, it is judged whether an engine have been braking or not on the basis of signals from an acceleration opening sensor 14 and a throttle opening sensor 16. In the case of 'YES', it is judged the slip of driving wheels are over or not from the slip rate of the driving wheels in the case where a flag FE showing during engine brake control is set beforehand, and engine brake control is carried out at the time of 'YES'. In the case where car body speed (car speed) obtained from the wheel speed of driven wheels is smaller than a referential value, a flag showing that driving wheel rotational speed is larger than a driven wheel rotational speed is re-set, and engine brake control is terminated.

Description

[0001]
BACKGROUND OF THE INVENTION
The present invention relates to a device for controlling vehicle behavior, and more particularly to a vehicle behavior control device characterized by control during engine braking.
[0002]
[Prior art]
Conventionally, on low friction roads such as icing roads, when the throttle is returned and engine braking is applied, the rotational speed of the drive wheels is greatly reduced with respect to the vehicle body speed, so the drive wheels may slip. And if this drive wheel slips, the phenomenon that the lateral force of a drive wheel will reduce will generate | occur | produce.
[0003]
However, as shown in FIG. 1A, for example, when the vehicle turns, if the slip increases due to the engine brake and the lateral force of the drive wheels decreases as described above, a rotational moment is generated in the FR vehicle, and the vehicle May become unstable and cause tuck-in or spin. The FF vehicle does not spin, but the rudder may not work.
[0004]
As a countermeasure, a technique has been proposed in which the engine braking force is reduced by controlling the engine output to increase based on the engine output state and lateral acceleration, thereby controlling the wheel slip ratio within a predetermined range. (Refer to Unexamined-Japanese-Patent No. 62-153533).
[0005]
[Problems to be solved by the invention]
However, in the above-described control, the engine output is increased to prevent spin or tuck-in during engine braking, so the vehicle stability may be improved to some extent, but the driver expects There was a problem that deceleration could not be realized.
[0006]
Therefore, an object of the present invention is to provide a vehicle behavior control device that can realize both the stability of the vehicle and the deceleration expected by the driver.
[0007]
[Means for Solving the Problems]
In the first aspect of the invention, under the condition that the wheel speed of the driving wheel is reduced by the engine brake, the driving wheel control for adjusting the braking force to the driving wheel by the engine brake is performed, and the wheel speed of the driven wheel by the brake actuator is set. Drive wheel control to reduce.
[0008]
Therefore, for example, when trying to obtain vehicle deceleration by applying engine braking during a turn, conventionally, in order to prevent vehicle instability such as spin and tuck-in, control is simply performed to increase the engine output. However, according to the present invention, at that time, for example, the engine output is increased (the slip of the drive wheel is reduced) to perform the drive wheel control for increasing the lateral force, and the brake actuator such as a hydraulic brake is used. The driven wheel is controlled by applying a brake to the driven wheel.
[0009]
  This point will be described with reference to FIG. 1. For example, in a FR vehicle (rear wheel drive), in a situation where the vehicle tends to become unstable, such as when turning (or when driving on an icy road or a low friction road), for example, As shown in the conventional example of FIG. 1A, not only a large engine brake is applied to the drive wheels, but also the engine output is increased (that is, the engine brake is reduced) as illustrated in FIG. 1B, for example. Drive wheel controlGoThe lateral force is increased to reliably prevent the vehicle from becoming unstable such as spinning and tuck-in. At the same time, by braking the driven wheel, there is a remarkable effect that safe and sufficient braking can be performed without significantly reducing the deceleration of the vehicle body.
  In the present invention, the distribution of the braking force in the drive wheel control and the driven wheel control is adjusted according to the slip state of the wheels.
For example, when the wheel slip is excessive, it is considered that braking by the engine brake is excessive and the lateral force at the driving wheel is greatly reduced. In such a case, the engine braking force is reduced and the driven wheel is reduced. By increasing the braking force, the vehicle can be stabilized and the vehicle body deceleration can be increased. On the other hand, if the wheel slip is small even when the engine brake is applied, it is determined that the lateral force on the driving wheel is reduced little, so that the engine braking force is maintained (or increased) and the braking force on the driven wheel is reduced. The vehicle stability can be reduced and the vehicle body deceleration can be increased.
[0010]
In the invention of claim 2, as the drive wheel control, control is performed to reduce the braking force by the engine brake by increasing the engine output.
That is, when the engine brake is too effective, as described above, the engine output is increased to reduce the braking force by the engine brake. Thereby, the slip of the driving wheel is reduced and the lateral force is increased, so that the stability of the vehicle body is improved.
[0012]
  Claim3In this invention, when a predetermined slip or more occurs on the driving wheel due to the engine brake, the driving wheel control and the driven wheel control are performed.
  As shown in FIG. 2, the friction coefficient of the wheel changes according to the slip ratio of the wheel. Specifically, on dry roads and icy roads, the friction coefficient in the front-rear direction reaches a peak at a predetermined slip ratio, and the friction coefficient in the lateral direction decreases as the slip ratio increases. The vehicle is divided into a stable region and an unstable region.
[0013]
In other words, when the engine brake causes a slip more than a predetermined value on the drive wheels, the lateral force is reduced and the vehicle is in an unstable state. In order to prevent this, the vehicle body deceleration can be increased in a stable traveling state of the vehicle by performing the driving wheel control for reducing the engine brake and the driven wheel control by the brake actuator.
[0014]
  Claim4In this invention, the braking force at the time of engine braking is distributed to the braking force in driving wheel control and driven wheel control within a range where the vehicle is stable.
  For example, as shown in the braking force distribution diagram of FIG. 3 (a), in an FR vehicle, the vehicle is separated by the distribution of the driving wheel braking force (rear braking force) and the driven wheel braking force (front braking force). It is determined whether it becomes stable or unstable. Therefore, the vehicle can be maintained in a stable state by adjusting the distribution between the rear braking force and the front braking force. Therefore, in the present invention, the braking force in the drive wheel control and the driven wheel control is distributed so as to be in the stable range.
[0015]
  In FIG. 3B, when point A is engine brake only, point B is only controlled to reduce engine brake, point C is driven wheel control and hydraulic brake for increasing engine output. An example in the case of performing driving wheel control is shown.
  Claim5In this invention, the distribution of the braking force by the drive wheel control and the driven wheel control is an ideal braking force distribution that can obtain a deceleration equivalent to the engine brake.
[0016]
This ideal braking force distribution is a boundary portion between the vehicle unstable region and the stable region, as indicated by a point C in FIG. That is, as shown in FIG. 3 (b) in an enlarged view of the main part of FIG. 3 (a), an unstable area where the rear wheel speed is smaller than the front wheel speed and a stable area where the rear wheel speed is larger than the front wheel speed This is a boundary portion (region where the front wheel speed and the rear wheel speed are substantially equal) indicated by hatching. Therefore, in the present invention, the highest braking force can be obtained while maintaining the stability of the vehicle.
[0017]
As can be seen from FIG. 3B, at the point C of the ideal braking force distribution, it can be seen that a part of the rear braking force ΔBr is directly replaced by the front braking force ΔBf. In other words, in the present invention, the reduced amount of braking by the engine brake is directly replaced with the brake control of the driven wheel.
[0018]
  Claim6In the invention, when the operation of applying the engine brake is an operation by the driver's accelerator operation, the driving wheel control and the driven wheel control are executed.
  Therefore, when the driver tries to reduce the vehicle speed by returning the accelerator pedal, for example, when turning or on an icy road or a low friction road, the deceleration expected by the driver is ensured while ensuring the stability of the vehicle. There is an effect that can be realized.
[0019]
  Claim7In this invention, when the engine brake is automatically applied, for example, when the throttle is automatically returned and the brake is actively applied like the automatic brake, or the throttle is automatically returned to reduce the engine output like the automatic throttle control. When the engine brake is applied, the drive wheel control and the driven wheel control are executed.
[0020]
  Therefore, as in the case of the sixth aspect, when the engine brake is automatically applied, for example, when turning, icing road, low friction road, etc., sufficient deceleration can be realized while ensuring the stability of the vehicle. There is an effect.
[0021]
DETAILED DESCRIPTION OF THE INVENTION
Next, an example (example) of an embodiment of the present invention will be described with reference to the drawings.
a) First, the overall configuration of the vehicle behavior control device of this embodiment will be described.
[0022]
As shown in FIG. 4, the present embodiment is applied to a front engine / rear drive (FR) type vehicle using the internal combustion engine 2 as a power source.
As shown in FIG. 4, a surge tank 4 a that suppresses pulsation of intake air is formed in the intake passage 4 of the internal combustion engine 2, and a throttle valve 12 that is opened and closed by a throttle drive motor 10 is provided upstream thereof. . The throttle valve 12 is not directly opened and closed by the accelerator 6, but is a so-called linkless throttle.
[0023]
The accelerator 6 and the throttle valve 12 are provided with an accelerator opening sensor 14 and a throttle opening sensor 16 for detecting the respective openings, and detection signals from these sensors are input to the drive control circuit 20. .
A fuel injection valve 24 that supplies fuel to the internal combustion engine 2 operates based on a fuel injection command from a known internal combustion engine control circuit 26. The fuel injection command is determined in conformity with the operating state of the internal combustion engine 2, and information from various sensors including the intake pressure sensor 28 that detects the pressure of the surge tank 4 a is received from the internal combustion engine control circuit 26. It is created by processing based on the fuel injection command program.
[0024]
The drive control circuit 20 performs drive wheel control and the like which will be described in detail later. In addition to the accelerator opening sensor 14 and the throttle opening sensor 16, the drive wheel control circuit 20 includes an engine speed. Detection signals from the sensor 30, the driven wheel speed sensors 32FL and 32FR, the driving wheel speed sensor 40, the transmission ratio sensor 42, and the acceleration sensor 44 are also input. The drive control circuit 20 drives the throttle drive motor 10 based on these input signals, and executes a process for controlling the opening degree of the throttle valve 12.
[0025]
Here, the engine rotation speed sensor 30 detects the rotation speed of the crankshaft 2 a of the internal combustion engine 2, and is also used to create a fuel injection command by the internal combustion engine control circuit 26.
The driven wheel speed sensors 32FL and 32FR are sensors for detecting the rotational speeds of the left and right driven wheels (front wheels) 22FL and 22FR, respectively. When performing traction control or the like, the detection signal is used to estimate the vehicle body speed of the vehicle. Used for
[0026]
The drive wheel speed sensor 40 is a sensor for detecting the average rotational speed (drive wheel speed) of the left and right drive wheels 22RL and 22RR, and the rotation of the crankshaft 2a is determined by the left and right drive wheels 22RL via the propeller shaft 34 and the differential gear 36. , 22RR is provided on the output shaft of the transmission 38.
[0027]
The gear ratio sensor 42 is for detecting the gear ratio of the transmission 38 and is provided in the transmission 38 in the same manner as the drive wheel speed sensor 40.
b) Particularly in the present embodiment, as described below, a braking force control device 50 capable of performing driven wheel control is provided. In the present embodiment, even when the brake pedal 6 is not depressed, a well-known traction control that can apply braking to each of the wheels 22FL, 22FR, 22RL, and 22RR (collectively referred to as 22), and the brake pedal 6 An apparatus capable of performing anti-skid control at the time of depression will be described as an example. However, any apparatus that can apply braking to at least the driven wheels (front wheels 22FL, 22FR) may be used.
[0028]
As shown in FIG. 5, the braking force control device 50 includes an X piping hydraulic circuit including piping systems of a right front wheel 22FR-left rear wheel 22RL and a left front wheel 22FL-right rear wheel 22RR. The braking force that suppresses the rotation of the wheel 22 is controlled by adjusting the pressure (wheel cylinder pressure) applied to the 22 wheel cylinders 51FL, 51FR, 51RL, 51RR (collectively referred to as 51).
[0029]
Among the piping systems, a high hydraulic pressure is applied to the three-way switching valve 54A used for switching the hydraulic circuit (switched to two positions) and the front wheel 51FL to the pipe 53A1 from the master cylinder 52 to the wheel cylinders 51RR and 51FL. Proportional valve 55A, pressure increase control valves 56 and 57 for controlling the opening and closing of the pipeline from the master cylinder 52 side to the wheel cylinders 51RR and 51FL, and the pressure reducing control for controlling the opening and closing of the pipeline extending from the wheel cylinders 51RR and 51FL to the reservoir 66A A reservoir 66A for accumulating brake oil from the valves 61 and 62 and the wheel cylinders 51RR and 51FL, and a pump 67A for pumping the brake oil from the reservoir 66 to the master cylinder 52 side are provided. Further, in the pipe line 53A2 extending from the master reservoir 69 to the three-way switching valve 54A, a pressure control for controlling opening / closing of a pump 71A for increasing the brake hydraulic pressure, and a pipe line between the downstream side of the pump 71A and the master reservoir 69. A valve 72A is provided.
[0030]
Among these, when the three-way switching valve 54A is switched to the A position, the brake operation by a normal driver, the pressure increase control valves 56 and 57, the pressure reduction control valves 61 and 62, the reservoir is performed in the pipe A1. It is possible to perform known anti-skid control using the 66A, the pump 67A, and the like. On the other hand, when the position is switched to the B position, the well-known traction control and the driven wheel control of this embodiment can be performed by the high brake hydraulic pressure by the pump 71A.
[0031]
In the piping system, the other pipe line 53B1 from the master cylinder 52 to the wheel cylinders 51FR and 51RL has a three-way switching valve 54B, a proportion valve 55B, which can be switched to two positions, like the pipe line 53A1. Pressure increase control valves 58 and 59, pressure reduction control valves 63 and 64, a reservoir 66B, and a pump 67B are provided. Further, similarly to the pipe 53A2, a pump 71B and a pressurization control valve 72B are provided in the pipe line 53B2 from the master reservoir 69 to the three-way switching valve 54B.
[0032]
The braking force control device 50 having such a configuration is provided with a braking force control circuit 73 for controlling the driving thereof. The braking force control circuit 73 includes first and second pressure sensors 75 and 76 for detecting the hydraulic pressure between the three-way switching valves 54A and 54B from the pumps 71A and 71B in order to detect a braking state. Detection signals are input from the third and fourth pressure sensors 77 and 78 that detect the hydraulic pressure between the master cylinder 52 and the three-way switching valves 54A and 54B. Control signals are output to the pressure increase control valves 56 to 59, the pressure reduction control valves 61 to 64, the pressurization control valves 72A, 72B, 66A, 66B, and the pumps 71A, 71B in accordance with the braking state.
[0033]
c) Next, driving wheel control and driven wheel control (hereinafter collectively referred to as engine brake control) of this embodiment controlled by the driving force control circuit 20 and the braking force control circuit 73 will be described.
(1) First, the main routine of the engine brake control of this embodiment will be described based on the flowchart of FIG.
[0034]
In step 100, signals from various sensors are input.
In the following step 110, whether or not the engine brake (E / G brake) is currently being performed is determined based on, for example, a signal from the accelerator opening sensor 14 or the throttle opening sensor 16, and the accelerator 6 or the throttle valve 12 is returned. Judgment by whether or not. If an affirmative determination is made here, the process proceeds to step 120, while if a negative determination is made, the process proceeds to step 160.
[0035]
In step 120, whether or not the engine brake control is being performed is determined by whether or not the flag FE indicating that the engine brake control is being performed is set (whether it is 1). If an affirmative determination is made here, the process proceeds to step 160, while if a negative determination is made, the process proceeds to step 130.
[0036]
In step 130, it is determined from the slip ratio of the drive wheel whether the slip of the drive wheel is excessive. If an affirmative determination is made here, the process proceeds to step 140. If a negative determination is made, the process proceeds to step 170. The slip ratio of the drive wheel is obtained by dividing the difference between the rotation speed of the drive wheel and the rotation speed of the driven wheel by the rotation speed of the driven wheel.
[0037]
In step 140, the flag FE is set (set to 1), assuming that the condition for entering engine brake control is satisfied.
In the subsequent step 150, specific engine brake control, which will be described in detail later, is performed, and this process is temporarily terminated.
[0038]
On the other hand, in step 160 which proceeds with affirmative determination in step 120, it is determined whether or not the vehicle body speed (vehicle speed) obtained from the wheel speed of the driven wheel is smaller than the reference value KE. The process proceeds to step 170. On the other hand, if a negative determination is made, the process proceeds to step 150 to perform engine brake control. That is, when the vehicle speed is low, the vehicle does not become unstable, and therefore it is not necessary to perform engine brake control. Therefore, this determination determines whether or not engine brake control is necessary. .
[0039]
In step 170, a flag FB indicating that the driving wheel rotational speed described later is larger than the driven wheel rotational speed is reset, and a flag FE indicating that engine brake control is being performed is also reset.
In subsequent step 180, in order to stop (or not start) the engine brake control, for example, the target value of the throttle opening is set to 0, the pumps 71A and 71B, the three-way switching valves 54A and 54B, and the pressurization control valve 72A. , 72B is turned off, engine brake control is initialized, and the process is temporarily terminated.
[0040]
As described above, in this main routine, when the start or end of engine brake control is determined and a predetermined condition is satisfied, the engine brake control can actually be performed.
(2) Next, the engine brake control executed in step 150 will be described based on the flowchart of FIG.
[0041]
In step 200, the wheel speed difference DFR is calculated by subtracting the driving wheel speed VR from the driven wheel speed VF. For the driven wheel speed VF, an average value of the left and right driven wheel speeds is obtained. In step 210, it is determined whether or not the flag FB has already been set, that is, whether or not the driving wheel speed VR has already been greater than the driven wheel speed VF. If an affirmative determination is made here, the process proceeds to step 250, whereas if a negative determination is made, the process proceeds to step 220.
[0042]
In step 220, it is determined for the first time whether or not the wheel speed difference DFR is negative, that is, whether or not the driving wheel speed VR is greater than the driven wheel speed VF. If an affirmative determination is made here, the process proceeds to step 250, whereas if a negative determination is made, the process proceeds to step 230.
[0043]
In other words, since the engine is currently being braked, if the driving wheel speed VR is not greater than the driven wheel speed VF (that is, if a negative determination is made in step 220), the engine braking is effective. Therefore, it is determined that the condition for executing the engine brake control is satisfied.
[0044]
Accordingly, in step 230, as will be described in detail later, driving force increase control (part of driving wheel control) is executed to increase engine output and increase vehicle stability.
In the subsequent step 240, as will be described in detail later, braking is performed by increasing the wheel cylinder pressure of the driven wheel and braking is performed to prevent the deceleration of the vehicle body from being reduced (driven wheel control).
[0045]
Further, in step 250, which proceeds with an affirmative determination in steps 210 and 220, the flag FB is set.
In the following step 260, it is determined whether or not the wheel speed difference DFR is negative. If an affirmative determination is made here, the process proceeds to step 270, whereas if a negative determination is made, the process proceeds to step 290.
[0046]
In step 270, it is determined whether or not the absolute value of the wheel speed difference DFR is smaller than the reference value KV2. If an affirmative determination is made here, the present process is once terminated, whereas if a negative determination is made, the process proceeds to step 280.
That is, the case where the determination in steps 260 and 270 is followed to reach step 280 is a case where the driving wheel speed VR is considerably larger than the driven wheel speed VF and the driving force is considered to be excessive.
[0047]
Therefore, in step 280, as will be described in detail later, driving force reduction control (a part of driving wheel control) for reducing the engine output is performed, and this processing is temporarily ended.
In step 290, where it is determined in step 260 that the driven wheel speed VF is greater than or equal to the driving wheel speed VR, it is determined whether or not the wheel speed difference DFR is greater than the reference value KV1. If an affirmative determination is made here, the present process is temporarily terminated, whereas if a negative determination is made, the process proceeds to step 295.
[0048]
That is, the case in which the determination in steps 260 and 290 is followed to reach step 295 is a case where the driving wheel speed VR is considerably smaller than the driven wheel speed VF and the driving force is considered to be too small.
Accordingly, in step 295, the above-described driving force increase control for increasing the engine output is performed, and this process is temporarily terminated.
[0049]
(3) Next, the driving force increase control performed in steps 230 and 295 will be described based on the flowchart of FIG.
In step 300, wheel torque change request amount ΔT is set to KT (positive value). Here, KT is a torque increase / decrease amount that increases / decreases for each control cycle, and may be a fixed value or may be obtained from a map of wheel speed difference DFR-KT as shown in FIG. 9A, for example.
[0050]
In the subsequent step 310, a target opening degree calculation process, which will be described later, is performed to calculate a target opening degree TH of the throttle valve 12, and this process is temporarily terminated.
(4) Next, the target opening degree calculation process performed in step 310 will be described based on the flowchart of FIG.
[0051]
In step 400, an engine shaft torque estimated value Taxe is calculated from the current engine speed and throttle opening using the map showing the relationship between the engine shaft torque, engine speed, and throttle opening shown in FIG. 9B.
In the subsequent step 410, the value of ΔT set in step 300 is substituted into the following equation (1) to calculate the engine shaft torque change amount request value ΔTaxe.
[0052]
ΔTaxe = ΔT / (Im · If) (1)
However, Im: Transmission gear ratio, If: Final gear ratio
In subsequent step 420, the map shown in FIG. 9B is used to determine the throttle opening TH from the current engine speed and the target value (Taxe + ΔTaxe) of the engine shaft torque, and this process is temporarily terminated.
[0053]
Therefore, in the driving force increase control shown in FIGS. 8 (a) and 8 (b), the engine output is increased to drive to a desired value by controlling the throttle opening TH obtained in step 420. The power can be increased (ie, the engine brake can be reduced).
[0054]
(5) Next, the driving force reduction control performed in step 280 will be described based on the flowchart of FIG.
In step 500, the wheel torque change request amount ΔT is set to −KT (negative value). Here, KT is the same as the value in step 300.
[0055]
In the subsequent step 510, the target opening degree calculation process described with reference to FIG. 8B is performed to calculate the target opening degree TH of the throttle valve 12, and this process is temporarily terminated. Therefore, in this driving force reduction control, the engine output is decreased by controlling the throttle opening TH obtained in step 510 to reduce the driving force to a desired value (that is, increase the engine brake). )be able to.
[0056]
(6) Next, the braking force increase control performed in step 240 will be described based on the flowchart of FIG.
In step 600, wheel torque change request amount ΔT is set to KT (positive value). Here, KT is the same as the value in step 300.
[0057]
In the subsequent step 610, the value of ΔT set in step 600 is substituted into the following equation (2) to calculate the required hydraulic pressure change amount ΔP.
ΔP = ΔT / (2 · μ · r · Aw) (1)
Where μ: friction coefficient between brake pad and rotor
r: Effective rotor radius
Aw: Wheel cylinder cross-sectional area
In the following step 620, the solenoid request value T1, that is, the time for which the driven wheel pressure increase control valves 57 and 58 are turned on is calculated, and this process is temporarily terminated. Specifically, as shown in FIG. 11, a map indicating the relationship between the hydraulic pressure change requirement value ΔP and the solenoid demand value T1 is used, and the solenoid demand value T1 is calculated from the oil pressure change amount demand value ΔP obtained in step 610. [Ms] is obtained.
[0058]
That is, the larger the solenoid requirement value T1, the longer the valve opening time of the pressure increase control valves 57, 58, so that the higher hydraulic pressure increased by the pumps 71A, 71B is supplied to the wheel cylinders 51FL, 51RL of the driven wheels, The braking force increases.
In particular, in this embodiment, in order to obtain the ideal braking force distribution (for example, point C) shown in FIG. 3, the rear braking force that is reduced by the driving force increase control and the front braking force that is increased by the braking force increase control are The distribution is adjusted. Specifically, the engine of the drive wheel corresponding to the increase in engine output is set such that the required amount of wheel torque change ΔT in the driving force increase control and the required amount of wheel torque change ΔT in the braking force increase control coincide with each other. The decrease in the braking force is made to coincide with the braking force due to the increase in the brake hydraulic pressure of the driven wheel.
[0059]
d) Next, the operation by the above-described drive wheel control and driven wheel control will be described based on the explanatory diagram of FIG.
As shown in FIG. 12, when the accelerator pedal 6 is returned and the engine brake is applied at time t1, the driving wheel speed gradually decreases.
[0060]
Then, when the slip ratio (corresponding to the difference between the driving wheel speed and the driven wheel speed) exceeds the reference value at the time t2, the engine brake control of this embodiment is started. Specifically, the throttle opening is gradually increased to perform driving force increase control, and the brake hydraulic pressure of the driven wheel is gradually increased to perform braking force increase control. By performing this driving force increase control, the driving wheel speed gradually increases, and by performing the braking force increase control, the driven wheel speed gradually decreases.
[0061]
At time t3, the driving wheel speed is greater than the driven wheel speed. At time t4, the driving wheel speed is greater than the driven wheel speed by a predetermined value KV2 or more, and it is determined that the engine output is excessive. Therefore, the throttle opening is reduced and the braking force of the driven wheel is maintained. To do.
[0062]
Next, at the time t5, on the contrary, the driving wheel speed becomes smaller than the driving wheel speed by a predetermined value KV1 or more, and it is determined that the engine brake is excessive, so the throttle opening is increased.
As described above, in this embodiment, when the slip ratio exceeds the reference value, the driving force increase control for the driving wheel and the braking force increase control for the driven wheel are performed. At the same time, when the increase in engine output by the driving force increase control is excessive, the engine output is reduced. Conversely, when the engine brake is excessive, the engine output is increased.
[0063]
By performing this engine brake control, the vehicle deceleration can be kept higher than before without destabilizing the vehicle. Therefore, it is possible to realize stable running and high braking performance when turning or on a low friction road such as an icy road.
[0064]
Also, in this embodiment, the engine braking reduction due to the increase in engine output is compensated by the braking force applied to the driven wheel to provide ideal braking force distribution, so the vehicle body expected when the driver applies engine braking There is an advantage that a vehicle body deceleration similar to the deceleration can be obtained.
[0065]
The embodiments of the present invention have been described above. However, the present invention is not limited thereto, and it is needless to say that the present invention can be implemented in various forms without departing from the scope of the invention.
(1) For example, in the above-described embodiment, the case where the accelerator pedal is returned and the engine brake is applied is given as an example. However, the present invention can be applied to the case where the engine brake is automatically applied. . For example, the present invention can be applied to a case where control (automatic brake control, automatic throttle control) for automatically returning the throttle and applying a brake is performed.
[0066]
(2) Moreover, in the said Example, when the slip ratio became more than predetermined value, engine brake control was started, However, You may perform control which considered the road surface (micro | micron | mu) further. In this case, for example, when the road surface μ is small, there is a possibility that the slip may increase, so that the timing for starting the engine brake control may be advanced.
[0067]
(3) In the above embodiment, the FR vehicle has been described as an example, but the same engine brake control can be performed for the FF vehicle. That is, the same drive wheel control is performed on the front wheels that are drive wheels, and the same driven wheel control is performed on the rear wheels that are driven wheels. As a result, the slip ratio of the drive wheel is reduced, the lateral force is increased, and the braking force on the driven wheel is increased. Therefore, stable high braking performance can be exhibited without causing tack-in or the like.
[Brief description of the drawings]
FIG. 1 is an explanatory view for explaining the invention of claim 1 in comparison with the prior art.
FIG. 2 is a graph showing μ-S characteristics.
FIG. 3 is an explanatory diagram showing a relationship between a rear braking force and a front braking force.
FIG. 4 is a schematic configuration diagram of a vehicle behavior control device according to the present embodiment.
FIG. 5 is an explanatory diagram showing a hydraulic circuit and a control device of the braking force control device.
FIG. 6 is a flowchart showing a main route of engine brake control processing.
FIG. 7 is a flowchart showing an engine brake control process.
8A and 8B show a part of the engine brake control process, where FIG. 8A is a flowchart showing a driving force increase control process, FIG. 8B is a flowchart showing a target opening degree calculation process, and FIG. 8C is a driving force decrease control process. It is a flowchart to show.
9A is a graph showing the relationship between wheel speed difference and KT, and FIG. 9B is a graph showing the relationship between engine shaft torque, engine speed and throttle opening.
FIG. 10 is a flowchart showing a braking force increase control process.
FIG. 11 is a graph showing a relationship between a required hydraulic pressure change value and a required solenoid value.
FIG. 12 is an explanatory diagram showing an operation by engine brake control.
[Explanation of symbols]
2 ... Internal combustion engine, 6 ... Accelerator,
10 ... Throttle drive motor, 12 ... Throttle valve,
14 ... accelerator opening sensor, 16 ... throttle opening sensor,
20 ... Driving force control circuit, 24 ... Fuel injection valve,
26 ... Internal combustion engine control circuit, 30 ... Engine rotation speed sensor,
32FR, 32FL ... driven wheel speed sensor, 40 ... driving wheel speed sensor,
50 ... braking force control device,
51RR, 51FL, 51FR, 51RL ... wheel cylinder,
54A, 54B ... three-way switching valve, 56, 57, 58, 59 ... pressure increase control valve,
61, 62, 63, 64 ... decompression control valve,
67A, 67B, 71A, 71B ... pump,
72A, 72B ... pressurization control valve, 73 ... braking force control circuit

Claims (7)

Drive wheel control for adjusting the braking force applied to the drive wheel by the engine brake under the condition that the wheel speed of the drive wheel is reduced by the engine brake and for reducing the wheel speed of the driven wheel by the brake actuator A vehicle behavior control device for performing
A vehicle behavior control device that adjusts the distribution of braking force between the driving wheel control and the driven wheel control in accordance with a slip state of a wheel.   2. The vehicle behavior control device according to claim 1, wherein the driving wheel control is control for reducing braking force by engine braking by increasing engine output.   3. The vehicle behavior control device according to claim 1, wherein the driving wheel control and the driven wheel control are performed when a slip of a predetermined value or more is generated on the driving wheel by the engine brake. 4.   The vehicle behavior according to any one of claims 1 to 3, wherein the braking force during the engine braking is distributed to the braking force in the driving wheel control and the driven wheel control within a range in which the vehicle is stable. Control device.   The vehicle behavior control device according to any one of claims 1 to 4, wherein the distribution is an ideal braking force distribution capable of obtaining a deceleration equivalent to an engine brake.   The vehicle behavior control device according to any one of claims 1 to 5, wherein the operation of applying the engine brake is an operation by a driver's accelerator operation. The vehicle behavior control device according to any one of claims 1 to 6, wherein the operation of applying the engine brake is an operation at the time of automatic control for automatically adjusting a driving force and a braking force .

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